An ancestral hard-shelled sea turtle with a mosaic of soft skin and scutes

The transition from terrestrial to marine environments by secondarily aquatic tetrapods necessitates a suite of adaptive changes associated with life in the sea, e.g., the scaleless skin in adult individuals of the extant leatherback turtle. A partial, yet exceptionally preserved hard-shelled (Pan-Cheloniidae) sea turtle with extensive soft-tissue remains, including epidermal scutes and a virtually complete flipper outline, was recently recovered from the Eocene Fur Formation of Denmark. Examination of the fossilized limb tissue revealed an originally soft, wrinkly skin devoid of scales, together with organic residues that contain remnant eumelanin pigment and inferred epidermal transformation products. Notably, this stem cheloniid-unlike its scaly living descendants-combined scaleless limbs with a bony carapace covered in scutes. Our findings show that the adaptive transition to neritic waters by the ancestral pan-chelonioids was more complex than hitherto appreciated, and included at least one evolutionary lineage with a mosaic of integumental features not seen in any living turtle.

Correlative imaging to resolve molecular structures in individual cells: Substrate validation study for super-resolution infrared microspectroscopy

Light microscopy has been a favorite tool of biological studies for almost a century, recently producing detailed images with exquisite molecular specificity achieving spatial resolution at nanoscale. However, light microscopy is insufficient to provide chemical information as a standalone technique. An increasing amount of evidence demonstrates that optical photothermal infrared microspectroscopy (O-PTIR) is a valuable imaging tool that can extract chemical information to locate molecular structures at submicron resolution. To further investigate the applicability of sub-micron infrared microspectroscopy for biomedical applications, we analyzed the contribution of substrate chemistry to the infrared spectra acquired from individual neurons grown on various imaging substrates. To provide an example of correlative immunofluorescence/O-PTIR imaging, we used immunofluorescence to locate specific organelles for O-PTIR measurement, thus capturing molecular structures at the sub-cellular level directly in cells, which is not possible using traditional infrared microspectroscopy or immunofluorescence microscopy alone.

Nano-Infrared Imaging of Primary Neurons

Alzheimer’s disease (AD) accounts for about 70% of neurodegenerative diseases and is a cause of cognitive decline and death for one-third of seniors. AD is currently underdiagnosed, and it cannot be effectively prevented. Aggregation of amyloid-β (Aβ) proteins has been linked to the development of AD, and it has been established that, under pathological conditions, Aβ proteins undergo structural changes to form β-sheet structures that are considered neurotoxic. Numerous intensive in vitro studies have provided detailed information about amyloid polymorphs; however, little is known on how amyloid β-sheet-enriched aggregates can cause neurotoxicity in relevant settings. We used scattering-type scanning near-field optical microscopy (s-SNOM) to study amyloid structures at the nanoscale, in individual neurons. Specifically, we show that in well-validated systems, s-SNOM can detect amyloid β-sheet structures with nanometer spatial resolution in individual neurons. This is a proof-of-concept study to demonstrate that s-SNOM can be used to detect Aβ-sheet structures on cell surfaces at the nanoscale. Furthermore, this study is intended to raise neurobiologists’ awareness of the potential of s-SNOM as a tool for analyzing amyloid β-sheet structures at the nanoscale in neurons without the need for immunolabeling.

Correlative optical photothermal infrared and X-ray fluorescence for chemical imaging of trace elements and relevant molecular structures directly in neurons

Alzheimer's disease (AD) is the most common cause of dementia, costing about 1% of the global economy. Failures of clinical trials targeting amyloid-β protein (Aβ), a key trigger of AD, have been explained by drug inefficiency regardless of the mechanisms of amyloid neurotoxicity, which are very difficult to address by available technologies. Here, we combine two imaging modalities that stand at opposite ends of the electromagnetic spectrum, and therefore, can be used as complementary tools to assess structural and chemical information directly in a single neuron. Combining label-free super-resolution microspectroscopy for sub-cellular imaging based on novel optical photothermal infrared (O-PTIR) and synchrotron-based X-ray fluorescence (S-XRF) nano-imaging techniques, we capture elemental distribution and fibrillary forms of amyloid-β proteins in the same neurons at an unprecedented resolution. Our results reveal that in primary AD-like neurons, iron clusters co-localize with elevated amyloid β-sheet structures and oxidized lipids. Overall, our O-PTIR/S-XRF results motivate using high-resolution multimodal microspectroscopic approaches to understand the role of molecular structures and trace elements within a single neuronal cell.

Amyloid Structural Changes Studied by Infrared Microspectroscopy in Bigenic Cellular Models of Alzheimer's Disease

Alzheimer's disease affects millions of lives worldwide. This terminal disease is characterized by the formation of amyloid aggregates, so-called amyloid oligomers. These oligomers are composed of β-sheet structures, which are believed to be neurotoxic. However, the actual secondary structure that contributes most to neurotoxicity remains unknown. This lack of knowledge is due to the challenging nature of characterizing the secondary structure of amyloids in cells. To overcome this and investigate the molecular changes in proteins directly in cells, we used synchrotron-based infrared microspectroscopy, a label-free and non-destructive technique available for in situ molecular imaging, to detect structural changes in proteins and lipids. Specifically, we evaluated the formation of β-sheet structures in different monogenic and bigenic cellular models of Alzheimer's disease that we generated for this study. We report on the possibility to discern different amyloid signatures directly in cells using infrared microspectroscopy and demonstrate that bigenic (amyloid-β, α-synuclein) and (amyloid-β, Tau) neuron-like cells display changes in β-sheet load. Altogether, our findings support the notion that different molecular mechanisms of amyloid aggregation, as opposed to a common mechanism, are triggered by the specific cellular environment and, therefore, that various mechanisms lead to the development of Alzheimer's disease.

Synthesis and characterisation of isothiocyanate functionalised silicon nanoparticles and their uptake in cultured colonic cells

The functionalisation of silicon nanoparticles with a terminal thiocyanate group, producing isothiocyanate-capped silicon nanoparticles (ITC-capped SiNPs) has been successfully attained. The procedure for the synthesis is a two-step process that occurs via thermally induced hydrosilylation of hydrogen terminated silicon nanoparticles (H-SiNPs) and further reaction with potassium thiocyanate (KSCN). The synthesis was confirmed by Fourier transform infrared (FTIR) spectroscopy and X-Ray photoelectron spectroscopy (XPS). At the same time, the internalisation and the cytotoxicity of the ITC-capped SiNPs in vitro were assessed in two cell lines: Caco-2, human colorectal cancer cells and CCD-841, human colon "normal" cells. The results showed that above concentrations of 15 µg ml-1, the cell viability of both cell lines was depleted significantly when treated with ITC SiNPs, particularly over a 48 hour period, to approximately 20% cell viability at the highest treatment concentration (70 µg ml-1). Flow cytometry was employed to determine cellular uptake in Caco-2 cells treated with ITC SiNPs. It was observed that at lower SiNP concentrations, uptake efficiency was significantly improved for time periods under 12 hours; overall it was noted that cellular uptake was positively dependent on the period of incubation and the temperature of incubation. As such, it was concluded that the mechanism of uptake of ITC SiNPs was through endocytosis. Synchrotron FTIR spectroscopy, by means of line spectral analysis and IR imaging, provided further evidence to suggest the internalisation of ITC SiNPs displays a strong localisation, with an affinity for the nucleus of treated Caco-2 cells.

Soft-tissue evidence for homeothermy and crypsis in a Jurassic ichthyosaur

Ichthyosaurs are extinct marine reptiles that display a notable external similarity to modern toothed whales. Here we show that this resemblance is more than skin deep. We apply a multidisciplinary experimental approach to characterize the cellular and molecular composition of integumental tissues in an exceptionally preserved specimen of the Early Jurassic ichthyosaur Stenopterygius. Our analyses recovered still-flexible remnants of the original scaleless skin, which comprises morphologically distinct epidermal and dermal layers. These are underlain by insulating blubber that would have augmented streamlining, buoyancy and homeothermy. Additionally, we identify endogenous proteinaceous and lipid constituents, together with keratinocytes and branched melanophores that contain eumelanin pigment. Distributional variation of melanophores across the body suggests countershading, possibly enhanced by physiological adjustments of colour to enable photoprotection, concealment and/or thermoregulation. Convergence of ichthyosaurs with extant marine amniotes thus extends to the ultrastructural and molecular levels, reflecting the omnipresent constraints of their shared adaptation to pelagic life.

Correlating structure and electronic band-edge properties in organolead halide perovskites nanoparticles

After having emerged as primary contenders in the race for highly efficient optoelectronics materials, organolead halide perovskites (OHLP) are now being investigated in the nanoscale regime as promising building blocks with unique properties. For example, unlike their bulk counterpart, quantum dots of OHLP are brightly luminescent, owing to large exciton binding energies that cannot be rationalized solely on the basis of quantum confinement. Here, we establish the direct correlation between the structure and the electronic band-edge properties of CH3NH3PbBr3 nanoparticles. Complementary structural and spectroscopic measurements probing long-range and local order reveal that lattice strain influences the nature of the valence band and modifies the subtle stereochemical activity of the Pb(2+) lone-pair. More generally, this work demonstrates that the stereochemical activity of the lone-pair at the metal site is a specific physicochemical parameter coupled to composition, size and strain, which can be employed to engineer novel functionalities in OHLP nanomaterials.

Interpreting melanin-based coloration through deep time: a critical review

Colour, derived primarily from melanin and/or carotenoid pigments, is integral to many aspects of behaviour in living vertebrates, including social signalling, sexual display and crypsis. Thus, identifying biochromes in extinct animals can shed light on the acquisition and evolution of these biological traits. Both eumelanin and melanin-containing cellular organelles (melanosomes) are preserved in fossils, but recognizing traces of ancient melanin-based coloration is fraught with interpretative ambiguity, especially when observations are based on morphological evidence alone. Assigning microbodies (or, more often reported, their 'mouldic impressions') as melanosome traces without adequately excluding a bacterial origin is also problematic because microbes are pervasive and intimately involved in organismal degradation. Additionally, some forms synthesize melanin. In this review, we survey both vertebrate and microbial melanization, and explore the conflicts influencing assessment of microbodies preserved in association with ancient animal soft tissues. We discuss the types of data used to interpret fossil melanosomes and evaluate whether these are sufficient for definitive diagnosis. Finally, we outline an integrated morphological and geochemical approach for detecting endogenous pigment remains and associated microstructures in multimillion-year-old fossils.

Ultrastructural Heterogeneity of Carbonaceous Material in Ancient Cherts: Investigating Biosignature Origin and Preservation

Opaline silica deposits on Mars may be good target sites where organic biosignatures could be preserved. Potential analogues on Earth are provided by ancient cherts containing carbonaceous material (CM) permineralized by silica. In this study, we investigated the ultrastructure and chemical characteristics of CM in the Rhynie chert (c. 410 Ma, UK), Bitter Springs Formation (c. 820 Ma, Australia), and Wumishan Formation (c. 1485 Ma, China). Raman spectroscopy indicates that the CM has experienced advanced diagenesis or low-grade metamorphism at peak metamorphic temperatures of 150-350°C. Raman mapping and micro-Fourier transform infrared (micro-FTIR) spectroscopy were used to document subcellular-scale variation in the CM of fossilized plants, fungi, prokaryotes, and carbonaceous stromatolites. In the Rhynie chert, ultrastructural variation in the CM was found within individual fossils, while in coccoidal and filamentous microfossils of the Bitter Springs and formless CM of the Wumishan stromatolites ultrastructural variation was found between, not within, different microfossils. This heterogeneity cannot be explained by secondary geological processes but supports diverse carbonaceous precursors that experienced differential graphitization. Micro-FTIR analysis found that CM with lower structural order contains more straight carbon chains (has a lower R3/2 branching index) and that the structural order of eukaryotic CM is more heterogeneous than prokaryotic CM. This study demonstrates how Raman spectroscopy combined with micro-FTIR can be used to investigate the origin and preservation of silica-permineralized organics. This approach has good capability for furthering our understanding of CM preserved in Precambrian cherts, and potential biosignatures in siliceous deposits on Mars.

Molecular composition and ultrastructure of Jurassic paravian feathers

Feathers are amongst the most complex epidermal structures known, and they have a well-documented evolutionary trajectory across non-avian dinosaurs and basal birds. Moreover, melanosome-like microbodies preserved in association with fossil plumage have been used to reconstruct original colour, behaviour and physiology. However, these putative ancient melanosomes might alternatively represent microorganismal residues, a conflicting interpretation compounded by a lack of unambiguous chemical data. We therefore used sensitive molecular imaging, supported by multiple independent analytical tests, to demonstrate that the filamentous epidermal appendages in a new specimen of the Jurassic paravian Anchiornis comprise remnant eumelanosomes and fibril-like microstructures, preserved as endogenous eumelanin and authigenic calcium phosphate. These results provide novel insights into the early evolution of feathers at the sub-cellular level, and unequivocally determine that melanosomes can be preserved in fossil feathers.

Microspectroscopic evidence of cretaceous bone proteins

Low concentrations of the structural protein collagen have recently been reported in dinosaur fossils based primarily on mass spectrometric analyses of whole bone extracts. However, direct spectroscopic characterization of isolated fibrous bone tissues, a crucial test of hypotheses of biomolecular preservation over deep time, has not been performed. Here, we demonstrate that endogenous proteinaceous molecules are retained in a humerus from a Late Cretaceous mosasaur (an extinct giant marine lizard). In situ immunofluorescence of demineralized bone extracts shows reactivity to antibodies raised against type I collagen, and amino acid analyses of soluble proteins extracted from the bone exhibit a composition indicative of structural proteins or their breakdown products. These data are corroborated by synchrotron radiation-based infrared microspectroscopic studies demonstrating that amino acid containing matter is located in bone matrix fibrils that express imprints of the characteristic 67 nm D-periodicity typical of collagen. Moreover, the fibrils differ significantly in spectral signature from those of potential modern bacterial contaminants, such as biofilms and collagen-like proteins. Thus, the preservation of primary soft tissues and biomolecules is not limited to large-sized bones buried in fluvial sandstone environments, but also occurs in relatively small-sized skeletal elements deposited in marine sediments.

A 1:1 complex between a hydroxyl radical and ozone

A hydrogen bonded complex between a hydroxyl radical and ozone has been found in argon matrices at 9 K. The shift of the OH stretch (-12.6 cm-1) indicates that this complex is somewhat weaker than the OH-CO complex (-21.8 cm-1, D0<or=430 cm-1, 1.2 kcal/mol).

The vibrational spectrum of H2O3

This report presents positive infrared spectroscopic identification of H2O3, a higher oxide of hydrogen of importance for the understanding of the chain formation ability of atomic oxygen and a possible intermediate in hydrogen oxygen radical chemistry. All fundamental vibrations of H2O3, isolated in an argon matrix, have been observed. In addition, several bands of HDO3, D2O3, and H2(16)O2(18)O have been measured. One particular mode, the antisymetric O-O stretch at 776 cm-1, should be observable even in the presence of high water concentrations.

Automated in vitro dissolution rate analysis of potassium in plastic matrix slow release tablets

A fully automated system for dissolution rate analysis of potassium in slow release tablets is described. Aliquots are removed after 1, 2, and 4 hr from six samples, and potassium is analyzed in a flame photometer at 768 nm. A complete study of six samples takes 5.5 hr. The system may be run overnight. During the time intervals between the removal of aliquots, the system can be used for the determination of the total assay of tablets.